1. Field of the Invention
The present invention relates to a light guide panel for a backlight, which is used in a liquid crystal display device, and more particularly, the present invention relates to a light guide panel for a backlight, which minimizes loss of light introduced thereto and has various patterns on a surface thereof, thereby being able to ensure increased luminance and uniform distribution of luminance, through adjustment of a quantity of light, a scattering angle of light, etc.
2. Description of the Related Art
These days, a variety of displays have been disclosed in the art, and a typical example of these displays is a thin film transistor-liquid crystal display (TFT-LCD).
A liquid crystal display device is characterized as an optical element incapable of emitting light by itself, and therefore, in order to allow the liquid crystal display device to adequately perform its function, a backlight is provided.
Referring to FIG. 1, there is shown a perspective view schematically illustrating a construction of a conventional backlight for a notebook computer. As shown in FIG. 1, the conventional backlight 1 comprises a lamp 19 serving as a light source for emitting light, a light guide panel 13 for guiding and reflecting light emitted from the lamp 19 toward a LCD panel 18, a first diffusing sheet 14 for diffusing at predetermined angles light exiting the light guide panel 13, vertical and horizontal prism sheets 15 and 16 for converging and transmitting diffused light toward the LCD panel 18, and a second diffusing sheet 17 for diffusing at preselected angles light having passed through the prism sheets 15 and 16. The LCD panel 18 is arranged on the second diffusing sheet 17. A reflecting sheet 12 and a case 11 are disposed under the light guide panel 13. The reflecting sheet 12 performs a function of reflecting light rays scattered by the light guide panel 13 in the direction toward the LCD panel 18 and thereby minimizing loss of light.
In addition to the backlight 1 for a notebook computer, various backlights such as for a monitor are disclosed in the art. While the backlights can be constructed in slightly different ways depending upon use, they adopt basically the same principle. For example, while the construction of the backlight 1 for a notebook computer is slightly different from that of a backlight for a monitor in respect of sheet arrangement, they adopt basically the same operational characteristics.
The light guide panel 13 is an essential component element in the construction of the backlight 1, and functions to scatter light emitted from the lamp 19 and transmit scattered light in the direction toward the LCD panel 18.
Referring to FIG. 2, there is shown a cross-sectional view illustrating the conventional light guide panel employed in the backlight shown in FIG. 1. As shown in FIG. 2, the conventional light guide panel 13 has planar lower and upper surfaces 131 and 132. Light emitted from the lamp 19 serving as a light source is incident on the lower surface 131, and the incident light is reflected upward. In this type of light guide panel 13, it was found that loss of light is remarkable, and luminance and luminance distribution uniformity are poor.
To solve these problems, a great deal of efforts have been attempted toward efficient use of light, and resultingly, a technique of forming micro protrusions on a lower surface of a light guide panel through a separate printing process is disclosed in the art.
FIG. 3 is a cross-sectional view illustrating another conventional light guide panel formed with micro protrusions. As shown in FIG. 3, micro protrusions 133 are formed on the lower surface 131 of the light guide panel 13. Due to the presence of the micro protrusions 133, scattering and scattered light reflection are promoted.
However, in the case of the light guide panel 13 which is formed with the micro protrusions 133, since the micro protrusions 133 are formed through an ultraviolet-curing printing method which uses pigments, they tend to absorb light. As a consequence, loss of light is still substantial, and it is impossible to secure high luminance and luminance distribution uniformity. Also, due to the fact that the micro protrusions 133 are formed using pigments tending to absorb light, a color intensity of light varies with the lapse of time, whereby a quality of the liquid crystal display device is deteriorated and a lifetime thereof is shortened.
To cope with these problems, attempts have been made to develop a printless type light guide panel which is manufactured without the need of implementing a printing process. In these attempts, micro protrusions are formed on a lower surface of a light guide panel by implementing an etching process on a surface of a mold or on the lower surface of the light guide panel.
In this technique for forming a light guide panel, although improvement is accomplished to some extent in terms of methodology, it is still impossible to secure high luminance and luminance distribution uniformity.
Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a light guide panel for a backlight, which scatters light emitted from a light source and transmits scattered light in the direction toward a LCD panel in such a way as to minimize loss of light, and at the same time, is able to perform light diffusing and converging functions.
In order to achieve the above object, according to the present invention, there is provided a light guide panel for a backlight, comprising: a plurality of groups of cells regularly or irregularly formed on at least one surface of the light guide panel, with each cell having regularly or irregularly arranged therein a plurality of micro cells.